


Innocence

by iinoyb



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap, Ectobiology, Grinding, M/M, Sexual Tension
Language: English
Status: Completed
Published: 2017-09-05
Updated: 2017-09-05
Packaged: 2018-12-24 08:06:23
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,903
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12008547
Author URL: https://archiveofourown.org/users/iinoyb/pseuds/iinoyb
Summary: Sans isn't as innocent as he seems to be. Papyrus takes a test in self-restraint and gets a failing grade. (Repost from my old account)





	Innocence

Somehow, somewhere, there was an unnamed cosmic deity having a good laugh at his expense.

Papyrus was sure of this fact. He was also sure that if Sans kept going like he was now, they would not reach their house before he snapped.

Seriously, where did his little brother get these kinds of ideas even from? Maybe he should cut off the undernet connection, because that's the only place Papyrus could think of where the younger skeleton would learn things like this.

Learn to eat nice-cream in such an erotic way, it looked more like Sans was going down on the most delicious cock he'd ever tasted.

And the way the yellow-orange treat left an unmistakable smear down the smaller's chin just added another edge of agony, to that which Papyrus is fairly sure is his own personal hell.

That's what you get for fucking your brother.

"You're making a mess." He says evenly, because just staying quiet and staring is getting incredibly awkward, and it's not like his sinning thoughts could get any worse.

A small blue tongue peeks out to lick at the smudge, and Sans looks up at him with huge innocent eyes. "Did I get it?"

Papyrus was wrong. Oh so wrong. This is infinitely worse.

"Uhm... No."

Sans looks almost crestfallen, so the tall skeleton bends forward and uses a finger to rub away the last bit of nice cream on his brother's chin, tracing his face softly.

He's already pulling back, hand moving to wipe the sticky stuff off on his hoodie, when Sans catches his wrists.

"Don't do that." The young monster chides mildly, and Papyrus almost says something about it him not being the one to do the laundry anyway, when Sans pulls the hand to his face.

And proceeds to put those sticky phalanges in his mouth, sucking gently.

Papyrus thinks he may just have come a little bit in his shorts just then.

The next moment Sans has let go of him, skipping ahead on the path, boots crunching softly on the fresh snow and blue bandana billowing out behind him like some type of weird cape.

"Come on, Pappy! The tacos are waiting."

Sans almost trips in his childlike excitement to get home sooner, eager to cook for his big brother like the responsible little skeleton he is.

Watching his young sibling like that, adorable and pure and just too good for this world, too good for him, Papyrus knows two things for certain.

There is nothing in the entire underground he loves more than Sans. There is nothing he wouldn't do just to ensure his happiness.

Also, he's a dirty sinner.

* * *

It's remarkably hard to walk when your magic insists on trying to manifest in the most embarrassing ways possible, but after what seems to him like forever, they finally reach Snowdin's center.

Papyrus tries hard to keep his cool (hah, see what he did there?), because no matter how carefree he is, even he can't live down the embarrassment that would be caused if anybody saw his current predicament.

Walking through he streets with a magical hard on is not his idea of having a good time.

Finally, FINALLY, the door closes behind the two brothers and Papyrus starts bee-lining his way to his room.

He has an urgent need and he needs to take care of it right now or he won't be responsible for the consequences.

Small skeleton hands grasp the hem of his orange hoodie, inhibiting his slightly desperate flight to sexual freedom.

Sans is using the eyes again.

"Pappy!" The way the name is spoken almost like a plea doesn't help Papyrus's predicament at all. "You promised you'd spend the entire day with me."

Right. He did promise that...

What the hell had he been thinking?

"Yeah, I know, but..." He starts, but Sans's eyesockets are big and round and have just the smallest hint of tears starting to form at the corners.

"Sure, bro, I'll help you cook." Papyrus hears himself say, and he hears the same sadistic deity from earlier laughing at his expense in the distance.

Sans brightens up almost too quickly, like shrugging off an act. The elder skeleton wonders if his younger brother can produce tears on command.

Surely he _could_ , but Sans wouldn't... Would he?

There is no time to ponder this question as Sans practically drags him to the kitchen, starting to meticulously lay out the needed ingredients.

Papyrus just slouches there, watching as his brother does his thing with everlasting energy.

It's incredibly cute, he thinks.

Then Sans takes off his scarf.

"B-Bro, What are you doing?" His voice sounds slightly higher than he intended it to, but it seems Sans didn't notice.

"I don't want it getting dirty." The small skeleton drapes the fabric over the back of one of the kitchen chairs, before coming to stand besides his brother.

There is now an exquisite part of clavicle right there in Papyrus's vision, peeking out from a gray shirt, and he dies a little bit more inside.

It's not even what one could consider a lewd body part, but the simple fact that something normally so hidden is suddenly laid bare before him, brings a flush to Papyrus's face.

Not to mention Sans's fidgeting makes his shirt shift minutely, small flashes of sternum and rib in the corner of Papyrus's eyesight.

He's such a fucking pervert.

* * *

The cooking goes by in a haze, the older monster trying to find an ideal balance between paying enough attention to know what Sans is saying, as the small skeleton instructs him in the best ways to smash vegetables, and not staring at those delectable bones.

5 minutes in and Papyrus is already debating whether to kill himself with a spoon to escape this torture.

His face feels hot and his soul is thrumming slightly faster, magic coursing through his very being.

If he doesn't do something soon he might just burst.

Surely Sans has noticed. You'd have to be particular daft not to.

On the other hand, he might just be totally oblivious.

While the two of them have been engaged in... 'unbrotherly conduct' for some time now, their sexual encounters were still few and far in between.

Papyrus wasn't even sure if there had been any perceptible shift in their relationship. They have always been close, closer than regular brothers might be. It simply felt like the natural progressing of their relationship.

The sex was just a nice bonus.

And as such, he would always wait for the other to initiate it. Gentle, slow sessions of lovemaking, vanilla as people say.

Papyrus knows there is more... kinky stuff out there, but feels reluctant to bring it up. He would never allow anyone to hurt his brother, including himself.

And in the meantime, he can always _polish the bone_ himself, so to speak.

God, that was awful. He must be getting really desperate.

Probably because Sans is leaning in so close, touching his hands, voice almost husky.

Papyrus is fairly certain there isn't so much physical contact required to make a taco, but finds himself unable to say so.

Opening his mouth now is much more likely to produce some horribly embarrassing noise, so he clicks his jaw shut.

* * *

"We're done." Sans says at last, finally allowing Papyrus to regain his personal space when he brings the plates to the table.

The older skeleton sinks into his chair gratefully.

Right, he can do this. Just eat a taco, tell Sans his cooking is improving, wash away the terrible taco taste with a full bottle of honey, then say you really need to go take a shower.

He can do this...

He can do this...

He can't do this.

Not when Sans is running his foot slowly along his under the table. definitively moving upwards.

Papyrus breathes heavily, trying not to shiver as it nudges against his knee.

Sans is happily munching his taco, not a care in the world, for all intent and purposes unaware of how he's driving his brother crazy.

At least, that's what Papyrus tells himself. That Sans is totally unaware of what he does to him.

Until he feels that foot land in his lap, right against the straining erection already tenting the front of his trouser, still rubbing.

That's when he breaks.

The chair legs scrape against the ground harshly, entire thing almost toppling backwards.

Papyrus is on his baby brother in a second, all teeth and tongue as he almost smothers the smaller skeleton in kisses, eager hands enveloping that tiny body.

The way Sans reciprocates immediately, almost equally keen, only enhances the impression he may not be as innocent as he seems.

He uses his still seated position as an advantage, bringing his knee up to rub against Papyrus's groin again, and the older skeleton grunts at the pressure.

He switches them around easily, taking the seat for himself and heaving Sans into his lap, the younger brother's wriggling creating delicious friction against his member.

The lack of scarf allows him to run his tongue down the white expanse of neck in front of him, teasing the edges of the clavicle, making the younger monster shiver.

Sans grinds down hard in response, small gasps escaping him as blue magic begins to gather around him, mixing with orange.

Papyrus has his hands under his brother's shirt, rubbing the sensitive ribs hard, not in the mood to take it slow.

His soul feels like a fire raging inside his chest cavity, an intense feeling of warmth that spreads through his entire body, and he can see Sans's soul glowing in response.

When he manages to work his right hand up towards it, Sans keens at the touch.

"Ah- Nnn, Stars!" The small skeleton's eyes close in ecstasy as Papyrus rubs it harshly, fingers digging into the soft consistency.

His shifting becomes more desperate, grinding against his brother's dick in the most exquisite ways.

Papyrus keeps at it, tongue still working thoroughly at his siblings neck, intent to leave a mark.

The feelings are just too intense and Sans can't do much more but grasp his brother's shoulders harshly for leverage, pure rapture washing over him, moaning out his pleasure.

When he feels his older brother's teeth sink into the bones he breaks, soul gushing magic as he falls over the edge, pushing down harder than ever.

Papyrus's soul tightens in an instinctive reaction, feeling Sans's energy wash over him in pleasurable waves until he too is reaching climax, thoroughly ruining his pants in the process.

Both brothers just sit like that for a moment, conjoined magic slowly dispersing, waiting until their souls beat in a regular rhythm again.

The wet patch in his shorts feels slightly uncomfortable, especially as Sans shifts again, but Papyrus is frankly too lazy to do anything about it. Besides, the feeling of Sans's warmth against is chest is worth way more than ruined clothing.

"That took you long enough, Lazybones." Sans huffs, right at his ear hole.

Papyrus sighs in response. The moment he had felt that foot in his lap, it had all clicked inside his head.

Maybe he needs to reevaluate his brother's innocence.

Still, whatever indecent thoughts might be hiding below the surface, as Sans nuzzles him slightly, arms wrapped around the larger chest in front of him, Papyrus can't deny his little brother certainly is cute.

**Author's Note:**

> Also feel free to visit [my Tumblr](https://iinoyb.tumblr.com/about), I take requests!


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